Method of burning explosive gaseous mixtures



June 10, 1930. w M. HEPBURN 1,763,047

METHOD OF BURNING EXPLOSIVE GASEOUS MIXTURES Filed Oct. 28, 1927 I N VENTOR.

Wm. M HEPDU RN Z ,3 ATTORNEY.

Patented dune 10. 1930 UNITED STATES PATENT; OFFICE WILLIAM H. HEPIBUBN,OF TOLEDO, OHIO,

ASSIGNOR TO THE SURFACE COMBUSTION COMPANY, me, or TOLEDO, 0310; Aooarona'rron on NEW YORK Application filed Qctober 28, 1927. Serial 110.229,427.

This invention relates to imprvements in the art of burning explosivegaseous mixtures and has for its general object to provide an improvedmethod of and apparatusfor forming suchmixtures where the pressure ofthe fuel gas is sufficient to allow for entrainment of the full amountof air needed for combustion. Explosive mixtures will back flash andexplode if the rate of supply of the mixture to the burners falls belowthe rate of flame propagation through the mixture. \Vhile the volume ofthe mixture subject to explosion may not be such as to be hazardous Inevertheless the noise of the explosion is objectionable and tends toalarm the operator. Mixing tubes having a Venturi throat give highefficiencies of entrainment but on account of the objectionableexplosions which occur in case of back'fiash, the'use ofVenturi throatmixers is in practical operation limited to the relatively smallersizes. Instead of using Venturi throat mixing tubes where large volumesof explosive mixtures are to be burned a mixing tube known in the tradeas a '2 velocity burner has been developed. This velocity burnercomprises essentially a straight walled tube having a flared inlet endinto which a jet of gas is discharged for entraining the air requiredforcombustion, the discharge end of the tube being somewhat restrictedand the tube being only of a length to insure equalization of pressureof the mixture in the .tube. Explosions due to back fire are not asnoisy in velocity burners considering the capacity of the burners asinventuri throat mixers of like or even less capacity which is oneadvantage in their favor. However, velocity burners are not as eflicientas Venturi throat mixers, a fact which makes 49 it a matter of greatdifficulty to obtain proper proportions of air and light gases such ascoke oven gas.

One of the particular objects of the present invention is to provide anapparatus which will function efficiently over a wide range of operationand which may be operated in such a manner that explosion due to backflash shall be rendered unobjectional or practicallv eliminated.

Briefly stated the invention consists in a novel combination of aVenturi throat mixer and a velocity burner or an ejector tube soconstructed and arranged that the final explosive mixture results fromadmixture of gaseous bodies delivered from the two types of mixers.

Referring to the drawings forming part of this specification, Fig. 1 isa sectional view of one form of apparatus for practicing the inventionand Fig. 2 is a sectional view of a modified form of the apparatus, bothviews showing a fragmentary section of the furnace' wall through whichthe explosive mixture is introduced into the furnace for burnmg.

Only so much of a furnace as will suffice to illustrate the applicationof the invention has been shown, that is to say, a furnace wall 10provided with a combustion tunnelll. The burner head of the apparatus isa chamber generally indicated at 12 and its discharge nozzle at 13. Theburnerhead is secured. to the furnace wall in any suitable manner as bya radial flange 14.

Discharging into the burner head is a mixer tube 15'having a Venturithroat and discharging into the-entrance end or mouth of the mixer tubeis a spud or nozzle 16. ,Gas is supplied to the spud by a branch pipe 17leading from a main conduit 18, said branch having a valve 19 forcontrolling the flow of gas to the spud. Thegas discharged through thespud inspirates air as it passes into the mixer and the parts are soproportioned that the amount of air so inspirated will form with the gasa mixture which is too lean to burn. An air shutter 20 is shown asprovided in front of the entrance to the mixer tube. This shutter,however, will ordinarily only be used to close off theair flow whenstarting the burner in order that a pure gas or a rich gas-air mixturemay be present in the tube when lighting up. In regular operation,adjustment of the air shutter will not be 9 necessary becauseof the factthat the parts controlling the air gas ratio, that is to say, the sizeof the spud 16, the size of the Venturi throat of the mixer tube 15 andthe size of the burner nozzle will be so proportioned as to permit theformation of the desired lean mixture of air and gas.

The means for supplying the additional amount of fuel required to beadded to the lean mixture in order to form an explosive mixture forburning in the combustion tunnel 11 will now be described. Referring to'Fig. 1 there is'provided in the burner head chamber 1.2 a tube 22 whichmay for convenience be termed an ejector tube. This tube is shown asprovided with a flaring mouth and with a somewhat restricted outlet. Thelength of the tube may be such that its outlet terminates substantiallyflush with the burner nozzle 13 but it may be shorter and still functionproperly. The outer diameter of the tube should be such that a propersize annular space is formed between the burner nozzle 13 and theadjacent end of the tube in order that the mixture formed in the mixertube 15 may pass out through the burner nozzle under the entrainingaction of a stream of fuel gas or a mixture of fuel gas and air passedthrough the ejector tube.

Discharging into the ejector tube is a spud 24 which is supplied withgas by a branch pipe 26 leading from the main supply conduit 18, a valve28 being provided in the branch pipe for controlling the supply of gasto the spud. The spud 24 discharges into the ejector tube in a manner toallow air to be entrained by the jet of gas discharged from the spud.The amount of air so entrained will be less than is required to form anexplosive mixture in the ejector tube and more particularly will be suchthat upon admixture of the mixture formed in the mixer tube 15 and themixture formed in the ejector tube an explosive mixture will be formed.An air shutter 30 is provided in front of the mouth of the ejector tubebut under ordinary conditions of operation such shutter need not be usedbecause the ejector tube and its spud will be so proportioned withrespect to each other that for any given fuel gas a proper mixture willbe formed, that is to say, a mixture which is so rich in fuel gas as tobe nonexplosive. The air shutter 30 therefore finds its principal use inpreventing or regulating the entrainment of air in lighting up theburner.

In Fig. 2 I have shown the ejector tube as may be briefly described asfollows: The gas in the main supply conduit 18 is divided into two flowpaths 17 and 26, these streams becoming confluent in close proximity tothe burner nozzle 13. The gas discharged into the Venturi-throat mixertube 15 (15) entrains enough air to render the mixture nonexplosivelylean with resultant reduction in pressure head. The gas discharged intothe ejector tube 22 (Fig. 1) entrains some air but not euoiilgh to makethe mixture explosive, the amount of air so entrained being, however,such as will make the resultant admixture of the two separately formedmixtures explosive.

The gaseous mixture formed in the ejector tube 22 will of course beunder a greater pressure head than the mixture formed in the mixer tube15 and consequently the mixture discharged from the ejector tube willentrain the other mixture thus forming an explosive mixture. in closeproximity to the outlet end of the burner nozzle. The explosive mixtureburns in the combustion chamber 11 as will now be understood.

The mode of operation of the apparatus shown in Fig. 2 is the same inprinciple as that described in connection with Fig. 1, the onlydifference being that pure fuel gas instead of a diluted gas isdischarged from the ejector tube 22. It will now be seen that thedescribed apparatus permits the formation of an explosive gaseousmixture by means of two streams which eventually become confluent. thevelocity energy of at least one of said streams being utilized toentrain air in advance of the point of confluence of said streams, theamount of air so entrained beingin such "amount as to form anon-explosive lean mixture of fuel gas and air, the other stream beingutilized for entraining the non-explosive gaseous mixture thus formed,the resultant admixture being an explosive mixture.

While the invention finds its most importually become confluent,utilizing at least one of said streams for entraining air in advance ofthe point of confluence of said streams, and utilizing the other streamfor entraining the gaseous mixture formed as aforesaid.

2. A method of mixing fuel gas and air in given proportions comprisingdividing a stream of fuel gas into two branches, directing said branchesinto flow paths which eventually become confluent, utilizing at leastone of said streams for entraining air in advance ofthe confluence ofsaid' streams, and utiliz 7 her. a

ing the other stream for entraining the gaseous mixture formed asaforesaid. 4

3. A method of forming and burning explosive gaseous mixtures in amanner to prevent explosion and backfire comprising supplying to achamber opening on a zone of combustion a non-explosive lean mixture ofgaseous fuel and air, inducin a flow of said lean mixture from said chamer toward thecombustion zone bya stream of fuel gas sulficiently rich tobe non-explosive but which upon intermingling with the lean mixtureforms an explosive mixture and burning the' resultant mixture in thecombustion zone.

4. A method of forming and burning explosive gaseous mixtures comprisingdirecting two streams of one of vthe constituents of sad mixture alongflow paths which eventually discharge into a common chamber, utilizingone of said streams for entraining in advance of said chamber suchvolumes of the other constituent as will form therewith a mixture whichis not explosive but which when finally mixed with the other stream willform therewith an explosive mixture, directing said other stream towardsaid chamber in a manner to entrain the non-explosive mixture wherebythe resultant mixture will be explosive within said'chamber, and burningthe resultant'mixture within said chamber.

5. A method of mixing fuel gas and air and burning themixture comprisingdirecting two streams of gas along flow-pat s which eventually dischargeinto a combustion chamber, utilizing at least one of said streams forentraining air in advance of said chamber, utilizing the other streamfor entraining the gaseous mixture formed as aforesaid, and

urning the resultant mixture in said cham-,

6. A method of mixture of fuel gas and combustion support.- ing gas inapproximately constant proportion to a com ustion chamber, comprisingsupplying one of the gases und'era higher pressure than the other toserve as an inducsupplying an explosive supplying one of the gases undera hi her ressure than the other to serve as an 1n ucmg gas, changingsome of the pressure energy-of such inducing gas to veloc1ty energy withreduction of pressure, supplying t e other gas to the stream of theinducing gas at a point of relatively high velocity and vlow pressure,changing some of the velocity energy of the mixture back to gressureenergy, the relative'volumes of sai gases lacking those proportionsrequired for a substantial 1y correct mixture, and causing said mixtureto flow into said chamber by the inducing action of a stream of that gaswhich the mixture lacks to make a correct mixture, whereby the resultantmixture will be explosive.

In testimony whereof I aflix my signature.

WILLIAM M. HEPBURN.

the induced and inducing gases forming said mixture being in such\proportions as will make a non-explosive mixture, and causing 4 saidmixtureto flow into said chamber by the inducing action of a jet of gasof suc composition as will render the resultant mixture explosive uponreaching. said, chamber. v

7. A method of su plying an explosive mixture of fuel gas and combustionsupport ing gas in ap roximately constant proportion to a comustionchamber,comprising

